Process for maintaining high level of activity for supported manganese oxide acceptors for hydrogen sulfide



J. D. BATCHELOR ET AL A March 1', 1960 2,927,063 PROCESS FOR MAINTAININGHIGH LEVEL OF ACTIVITY FOR SUPPORTED MANGANESE OXIDE ACCEPTORS FORHYDROGEN SULFTIDE 2 Sheets-Sheet 1 Filed 061:. 28, 1957 HIGH SULFUR FLUEGAS AND so REGENERATED 1 REGENERATION AIR l I G. l

SOLIDS ACCEPTOR SULFIDED ACCEPTOR SOLIDS CARBONACEOUS NET GASDESULFURIZATION [l6 LOW SULFUR CARBONACEOUS HouRs 0F EXPOSURE TIME ATELEVATED TEMPERATURE IOO' RECYCLE GAS INVENTORS JAMES D. BATCHELORGEORGE P. CURRAN EVERETT GORIN March 1960 J. D. BATCHELOR ET AL2,927,063

PROCESS FOR MAINTAINING HIGH LEVEL OF ACTIVITY FOR SUPPORTED MANGANESEOXIDE ACCEPTORS FOR HYDROGEN SULFIDE Filed Oct. 28, 1957 2 Sheets-Sheet2 HIGH SULFUR NET CARBONACEOUS FLUE GAS GAS souos AND so 5 REGENERATED HACCEPTOR 2o E l2 l2 0 g x13 IB L DESULFURIZATION REGENERATION E s 2,9 AI A s I6 I? SULHDED I7 l9 'Q ACCEPTOR LOW SULFUR 8 AIR CARBONACEOUS o 22souos L E R FRESH 30 I NITRIC ACID I SUPPORTS 2 NON CONDENSI BLE NITRICACID GASES 4' 40 E.- A 36 1 24 2 MANGA SAIEJIESE FILTRATE LEACHINGVESSEL CONTINUOUS FILTER 33x3 32 REIMPREGNATED 39 ACCEPTOR I Go 2INVENTORS JAMES D. BATCHELOR GEORGE P. CURRAN EVERETT GORIN ATTORNEY2,927,063 Patented Mar. 1, 1960 PROCESS FOR MAINTAINING HIGH LEVEL OFACTIVITY FOR SUPPORTED MANGANESE X- lDE ACCEPTORS FOR HYDROGEN SULFIDEJames D. Batchelor, Bethel Park, and George P. Curran and Everett Gorin,Pittsburgh, Pa., assignors to Consolidation Coal Company, Pittsburgh,Pa., a corporation of Pennsylvania Application October 28, 1957, SerialNo. 692,865

12 Claims. (Cl. 20231) The present invention relates to a process formaintaining a high state of activity in supported manganese oxideacceptors for hydrogen sulfide. it relates to a process for removingsulfur contamination from carbonaceous solid materials by treatment withhydrogen in the presence of maganese oxide-type solid acceptors forhydrogen sulfide.

Such sulfur removal processes for carbonaceous solid fuels have beendescribed in copending U.S. patent application S.N. 527,705, now U.S.Patent 2,824,047, filed August 11, 1955 by Everett Gorin, George P.Curran and James D. Batchelor, assigned to the assignee of the pres entinvention. A further process relating to surfur removal and calcining ofcarbonaceous solid fuel briquets has been described in copending U.S.patent application S.N. 635,278 filed January 22, 1957 by James D.Batchelor, Everett Gorin, George P. Curran and Robert J.

taining manganese oxide impregnated on an inert sup port.

More particularly,

According to that process, carbonaceous solid fuels containing sulfurare mixed with a solid material (termed an acceptor) which is capable ofabsorbing hydrogen sulfide. The mixtureis treated with hydrogen gas at atemperature above about 1100 F. whereby the hydrogen gas combines withthe contaminating sulfur to form hydrogen sulfide; the hydrogen sulfideis absorbed in situ by the acceptor. Since the hydrogen sulfide isabsorbed almost instantly upon formation, there is only a negligiblepartial pressure of hydrogen sulfide in the desulfurization zone forinhibiting the reactions whereby sulfur is removed from the carbonaceoussolid fuels. The reaction mixture of solids is' separated into (a)product desulfurized carbonaceous solidfuels and '(b) the solid acceptorcontaining accepted sulfur. The acceptor may be regenerated and heatedby contact with air to restore its hydrogen sulfide acceptor propertiesthrough elimination of previously absorbed sulfur. The heatedregenerated acceptor, when mixed with relatively cool carbonaceous solidfuels preferably provides the heat necessary to raise the solidsreaction mixture to a desulfurization temperature.

Where the sulfur-containing carbonaceous solid fuel is V in the form offinely divided particles (e.g., fluidized low Friedrich, assigned to theassignee of the present invention.

The presence of sulfur in carbonaceous solid fuels limits their use inmetallurgical applications. Accordingly, most metallurgical fuels areobtained by employing low sulfur content starting materials, e.g., lowsulfur coal is converted to low sulfur metallurgical coke. Sulfurremoval processes of the type described in the aforementioned patentapplications permit the use of high sulfur content fuels as startingmaterials for preparing low sulfur content carbonaceous fuels formetallurgical use. For example, the sulfur removal process may beprovided as a treatment for the solid residue (termed char) resultingfrom low temperature carbonization of bituminous coal. Where fluidizedlow temperature carbonization processes are used, the finely divided,low density, porous char product is particularly amenable to thosedesulfurization treatments. The desulfurization treatment can be appliedto any non-caking carbonaceous solid fuel such as cokes and chars. Cokefrom coal and hydrocarbonaceous residues (pitch coke), coke breeze, lowtemperature carbonization char from coal and lignite are exemplary. Theprocesses cannot be applied to caking carbonaceous solid fuels such ascaking coal since the thermal treatment encompassed in such processeswould cause these materials to become sticky and form coked masses whichwould bind the acceptor solids, thus preventing their recovery for reusein the process. Further the resulting coke would be contaminated withthe acceptor solids; any sulfur transferred from the carbonaceous fuelsto the bound acceptor solids would remain in the solid coke. Theprocesses, however, are applicable to the desulfurization ofcarbonaceous briquets which may contain caking coal inter alia providedthe thermal treatment is conducted to avoid severecaking andaccompanying formation of large coke masses.

In the aforementioned copending application S.N. 527,705 solidcarbonized carbonaceous fuels are desulfurized by treatment at elevatedtemperatures in the presence of hydrogen and a solid acceptor forhydrogen The equilibrium ratio sulfide. A preferred acceptor inthis'proces's is one con- .Carbonaceous solid fuels contain sulfur in atleast three forms. Some of the sulfur exists as readily removable sulfurwhich -is organically bound in the carbonaceous fuel. This organicallybound sulfur can be removed from the carbonaceous solid fuels rathereasilyby contact with hydrogen. If the readily removable organicallybound sulfur is represented as C=S, the desulf ,furization reaction maybe represented as follows:

Some of the sulfur-exists as inorganic-ally bound sulfur usually intheform of metallic (principally iron) sulfide.

This. sulfur may. be-removed rather readily by treating the carbonaceoussolid fuel with pure hydrogen gas. The

reaction (assuming iron sulfide) is as follows:

' FeS-l-H eH s-i-Fe for reaction is very low. Hence small quantities ofhydrogen sulfide in the gas phase will inhibit the transfer of sulfurfrom the. solid to thegas. At 1350? F., for example, 0.12

volume percent of hydrogen sulfide in the hydrogen gas is theequilibrium value. At 1600 F., 0.28 volume per-' cent of hydrogensulfide in the hydrogen gas is the equilibrium value. Thus in ordertoremove inorganically bound sulfur effectively, the ratio of ,rnustbemaintained at an extremely low value, i.e., nearly 'purehydrogen must beused.

fur exists in the form of refractory organic material and variousinorganic sulfides. While this sulfur theoretically can be removed bytreatment of the carbonaceous solid fuels with pure hydrogen gas,nevertheless, even minute traces of hydrogen sulfide are sufiicient toinhibit the transfer of sulfur from the solids to the gas. Removal ofthe difficultly removable sulfur is not practicable under feasibleprocessing conditions.

The ultimate desulfurization which can be achieved at any temperaturedepends upon the ratio of in the treating gases without regard to theabsolute pressure of the reaction system. While greater absolutepressure increases the rate of desulfurization, it does not affect theultimate level of sulfur in the treated solids. In accordance with thesefindings, satisfactory desulfuri zation rates may be achieved attemperatures above about ll F. with atmospheric pressure. Higherpressure accomplishes the same desulfurization in shorter time. Apreferred pressure range for the desulfurization is about 1 to 6atmospheres absolute.

It is possible to maintain a low value for the ratio by employingenormous quantities of hydrogen as a treating gas. For example, the useof 1000 molar volumes of pure hydrogen gas in removing one mol of sulfurwould create an environment containing 0.10 volume percent of H 8 in HAlternatively, the ratio may be maintained at a low value by removingthe H 8 from the vapor state as quickly as it is formed. The removal ofH 8 from the vapor state can be accomplished by providing in adesulfurization zone a solid acceptor which has a greater aflinity forhydrogen sulfide than those materials with which the sulfur is bound inthe carbonaceous solid fuels. A preferred solid acceptor is onecontaining manganese oxide, impregnated on an inert carrier. Suitablecarrier materials include silica, alumina and silica-alumina preferablyin the form of mullite (containing 75 to 85 percent alumina and thebalance silica).

Acceptors containing manganese oxide are preferably prepared by soakingthe inert carrier particles in an aqueous solution of a solublemanganese salt which thermally decomposes to leave a residue ofmanganese oxide. Manganese nitrate is a preferred soluble salt forthis'purpose. The concentration of the aqueous solution should besuificient to deposit up to about 10 percent by weight of manganese onthe carrier. The soaked carrier thereafter is heated to achievedehydration and decomposition of the deposited manganese salt to themanganese oxide residue. The resulting acceptor should contain up toabout 10 percent by weight of manganese, preferably from about 4 toabout 8 percent.

Throughout the specification, the term manganese oxide refers tocompounds containing manganese and oxygen, such as MnO, M11 0 Mn 'O MnOwhich compounds are principally in the form of MnO. The term higheroxides of manganese refers to compounds containing more than one atom ofoxygen per ato'm of manganese, e.g., Mn O Mn O MnO- I The reaction ofthe manganese oxide in the disulfurization treatment is as follows:

MnO

Thus the manganese oxide combines with the generated hydrogen sulfide toform manganese sulfide thereby removing from the vapor phase thehydrogen sulfide formed by desulfurization of the carbonaceous solid:fueL

Thus in the overall process, the sulfur removed from the carbonaceoussolid fuels is rejected from the system in the form of sulfur dioxide.So much of the process has been more fully described in theaforementioned application, S.N. 527,705.

The use of H 8 acceptors has been briefly described in relation todesulfurization processes for carbonaceous solid fuels. Such H 8acceptors also can be used for removing H 5 from any gas stream,regardless of source. For example, elimination of H 8 from petroleumrefinery gases, pipeline gas, and the like can be accomplished bypassing the gases over an H s-acceptor containing manganese oxide. The H5 will be absorbed by the acceptor and the manganese oxide converted tomanganese sulfide. The sulfided acceptor can be regenerated by treatmentwith air to release sulfur dioxide and restore the manganese oxide.

The phrase H S-absorbing conditions as employed in this specificationrefers to a non-oxidizing environment containing H 8 at temperaturesWhere a favorable equilibrium exists for the reaction.

The preferred temperature range for H s-absorbing conditions is about1100 to 1600 F. The ability of an acceptor to react with H 3 under flS-absorbin'g conditions is an important determinant in the efiiciency ofthe fundamental desulfurization process.

We have found that repeated use of solid acceptors containing manganeseoxide impregnated on silica, alumina or silica-alumina carriers resultsin deactivation of the acceptor. A brief discussion will explain thedeactivation phenomenon.

Freshly impregnated acceptor so'lids will remove hydrogen sulfide gasfrom a vapor stream in intimate contact therewith at a determinablerate. Subsequent regeneration of the acceptor by reaction with air willrestore the manganese oxide. However the regeneration necessarily isconducted at elevated temperatures which bring about the deactivation ofthe acceptor (under H s-absorbing conditions). When the regeneratedmanganese oxide acceptor is employed to remove hydrogen sulfide from agas in contact therewith, a lower reaction rate will be observed.Repeated processing of the acceptor through the sulfiding andregenerating processes will result in further deactivation, i.e., acontinued lowering in the rate at which the manganese oxide will removehydrogen sulfide from a gas in contact therewith.

While the regenerated acceptor does not suffer a significant loss in itscapacity to absorb hydrogen sulfide, thereis nevertheless a lowering inthe rate at which the absorption of hydrogen sulfide occurs. Hence adistinction is made between (a) The capacity of a regenerated acceptorto absorb hydrogen sulfide and (b) The rate at which a regeneratedacceptor will absorb hydrogen sulfide.

The capacity for hydrogen sulfide absorption depends upon the quantityof manganese oxide present, whereas the rate at which hydrogen sulfidecan be absorbed depends upon a condition which is referred to herein asthe acceptors activity under H s-absorbing conditions.

Hence the term deactivation refersto a lowering of'this activity and theterm reactivation refers to an increasing of this activity.

Note that it is possible to have a fully regenerated acceptor (one inwhich all of the manganese sulfide has been converted to manganeseoxide) although that acceptor is deactivated, i.e., the regenerated.acceptor will absorb H 8 only at a diminished rate. Should such aregenerated (deactivated) acceptor be exposed to H 8- absorbingconditions for a sufiiciently long period of time, the quantity of H 5absorbed by it would depend solely on the quantity of manganese oxidewhich it contains. A reactivated, regenerated acceptor, on the otherhand," would absorb the same quantity of H 8 in a shorter period oftime. 1

It is believed that this deactivation of manganese oxide impregnatedcarriers results from'a physical migration of the manganese into thecarrier itself The penetration of the manganese into the carrier maysometimes be accompanied by chemical reaction resultingin the formationof manganese silicates and aluminates. Any manganese thus converted isremoved from the cyclic MnO-MnSMnOMnS et cetera reactions.

The principal object of the present invention is to pro is to provide aregeneration process for converting the manganese sulfide of a manganeseimpregnated acceptor to the desired manganese oxide with minimumdeactivation of the acceptor. A still further object is'to' provide ;adesulfurization process which employs manganese impregnated acceptorswhich can be recirculated throughout the pro'cess through sequentialsulfur absorbing and sulfur elimination without severe loss of activity(under H S-absorbing conditions).

Another object of this invention is to provide a proc ess formaintaining a high level of activity for manganese oxide acceptors whichprocess also provides fresh acceptor to compensate for any loss ofacceptor which may occur.

According to the present invention, a portion of the regeneratedmanganese acceptor followingfregeneration to the oxide form, isreactivated by leaching with a strong acid solution (preferablyconcentrated nitric acid) to restore the manganese to an aqueous solubleform for re-impregnation on the inert supports. The leaching is carriedout at an elevated temperature of about. 50 to 200 C. in a confinedvessel to prevent escape of acid vapors. Substantially all of themanganese contained in v the acceptor is dissolved in the strong acidsolution in the form of aqueous soluble manganese salts. The acceptorsolids at the same time are soaked in the strong acid solution ofmanganese salts, and thereby retain the desired quantity of manganese(up to about 10 percent by weight) in the form of manganese salts. 1 Thesoaked acceptor solids are recovered from the leaching stage andfiltered from the manganese salt solution which 'is returned to theleaching stage for reuse. The filtered acceptor solids containsufficient residual manganese saltsolution to provide the desiredimpregnation. The moist, filtered acceptor solids are heated to vaporizethe residual acid solution and convert the absorbed manganese salts tomanganese oxide. The gases and vapors are recovered and condensed. Thecondensed acid solution is available for reuse in the process. Wherenitric acid is employed, some decomposition to non-condensible nitrogenoxide occurs. The uncondensed nitrogen oxides are recovered from thenon-condensible gases by a water scrubbing treatment for reuse asnit'ricacid,

If desired, additional manganese compounds such as oxides or saltsdecomposable to oxides can be added to the acceptor stream underreactivation before or during the leaching treatment.v Additional inertsupports also may be added before or during'the leaching treatment. to

"prepare additional acceptor fertile-process."

We prefer to use concentrated nitric acid in the'present processalthough other strong acids such as sulfuric and hydrochloric can beadapted to the process, Nitricacid is preferred because of the ease ofdecomposition of manganese nitrate to manganese oxide and furtherbecause of the relative ease of recovering the acid and the. nitrogenoxides (formedby its decomposition) for reuse.

Moreover, nitric acid is particularly eflective in the leach{ Figure 1is a schematic flow diagram illustrating the reactivation process stepsembodied in the present invention; and i I Figure 3 is a graphicalrepresentation of the activity loss for manganese oxide-type acceptorsaccording to length of exposure to elevated temperatures.

The generalized flow sheet .of Figure 1 illustrates the manner in whichan acceptor desulfurization process can be carried out in a continuousmanner. A desulfurization zone.10 receives non-caking carbonaceoussolids containing sulfur through a conduit 11 and regenerated ac-.ceptor solids through a conduit 12. In this instance, the activeingredient of the acceptor solids is manganese oxide. A. hydrogen-richtreating gas consisting essentially of hydrogen is introduced into thedesulfurization zone 10 through a conduit 13'. .Additional gases,consisting of hydrogen gas, are autogenously produced throughdevolatilization of the carbonaceous solids at the elevated temperatureof the desulfurization z one 10. Under preferred operating conditionsthe autogenously produced devolatilization gases will be in sufficientquantity to provide the full hydrogen requirements for desulfurizationso that extrinsic hydrogen production is not required.

The desulfurization zone 10 is maintained at a tem-' perature from about1100 to about 1600 F. Below about 1100 F., the desulfurization rate islow. Operation above about 1600 F. requires excessive heat and alsopromotes rapid deactivation of the acceptor. The pressure levelpreferably is high enough to provide a hydrogen gas partial pressure ofat least one atmosphere. A total pressure of from one to 'sixatmospheres ispreferred. I v .A typical char (containing sulfur)produced by fluidized. carbonization of Pittsburgh Seam coal at 950 F.yields devolatilization gases containing 58.6 percent .hy- .drogen and24.8 percent methane at 1.3 atmospheresand 1350 F. The same char yieldsdevolatilization gases containing 48.7 percent hydrogen and 32.9 percentmethane at 3 atmospheres and 1350 F. v

- During, passage through the desulfurization zone 10, the treatinggases remove sulfur from the carbonaceous solid fuels 'formin-g hydrogensulfide. The H 8, upon formation, is at once absorbed by the solidacceptor and removed from the gas phase.

Gases are recovered from-the desulfurization zone'10 through a conduit14 and recirculated through conduit 13 for further contact withcarbonaceous solids undergoing desulfurization. A net product gas isremoved through a conduit 15; i

The required residence of carbonaceous solids in the ldesulfurizationzone 10 depends upon the lability of the contaminating sulfur and alsoupon the level of 'desul-' furization desired. It must be borne in mindthat the 'ult'imate' sulfur level of the product is determined by thelevel of H 8 contamination which the manganese oxide will maintain.Where the hydrogen partial pressure of the treating gases is about oneatmosphere or greater, satisfactory desulfurization can be achieved bysubjecting the carbonaceous solids to the desulfurization conditions fora period of about three hours or less. In creased absolute pressure, asalready pointed out, promotes more rapid desulfurization.

Desulfurized carbonaceous solids are removed from the desulfurizationzone 10 as product through a conduit 16. Sulfided acceptor is removedfrom a conduit 17 and passed to an acceptor regeneration zone 18. Air isintroduced into the regeneration zone 18 through a conduit 19 to raisethe temperature of the acceptor through combustion of sulfur along witha portion of the carbonaceous solids commingled therewith and to removesulfur therefrom through oxidation to sulfur dioxide.

The temperature within the regeneration zone 18 is maintained at about1300 to 1600 F. Hot flue gases containing sulfur dioxide are removedfrom the regeneration zone 18 through a conduit 20.

Excessive oxidation in the regeneration zone 18 should be avoided inorder to restrict the quantity of higher oxides of manganese produced.Ideally, some of the acceptor solids recovered from the regenerationzone should be in the form of MnS. By maintaining from about 2 to about15 percent of the manganese as. MnS after regeneration, the oxides ofmanganese can be main tained principally in the form of MnO rather thanas higher oxides such as Mn O or Mn O The presence of higher oxides ofmanganese in the desulfurization zone undesirably consumes hydrogen gaswithout accompanying sulfur removal as will be hereinafter described. Ingeneral, the amount of oxygen used in the regeneration zone 18 should bewithin about 20 percent of the stoichiometric quantity, which would berequired for oxidizing all of the MnS to MnO according to the equationabove.

Regenerated acceptor is returned to the desulfurization zone 10 throughthe conduit l2 without deliberate cooling to serve therein as a meansfor removing H 8 therefrom and to supply the heat requirements thereof.

When the desuifurization process is operated as described with anacceptor comprising manganese oxide impregnated on an inert carrier,deactivation of the acceptor will occur as a result of its thermalexposure. Accordto the present process as illustrated in Figure 2, theacceptor deactivation may be retarded. In Figure 2, the elements of theprocess relating to the desulfurization stage bear numeralscorresponding to those of Figure 1. Corresponding numerals identifycorresponding elements. Regenerated acceptor solids are introduced intothe desulfurization stage 10 through a conduit 12. Sulfided acceptorsolids comprising inert carriers containing manganese sulfide andmanganese oxide are recovered from the desulfurization stage 10 througha conduit i7. The sulfided acceptor is regenerated in the usual mannerby treatment with air at about 1300 to 1600 F. in the regeneration zone18.

A portion of the regenerated acceptor solids is withdrawn from theconduit 12 through a conduit 21 and cooled in a heat exchanger 22. Thecooled regenerated acceptor solids are introduced into a leaching vessel24 through a conduit 23 either continuously or batchwise. The leachingvessel 24 is constructed of materials resistant to the chemical attackfrom nitric acid solution and is adapted to confine a slurry of acceptorsupports in a nitric acid medium at temperatures from about 50 to about200 C. The leaching vessel 24 accordingly should be adapted to withstandinternal pres-sures of several atmospheres to confine the nitric acidand oxides of nitrogen. A mixing device such as rotatable stirring 8paddle 25 provides agitation for the contents of the leaching vessel 24.

Strong nitric acid solution, preferably commercial concentrated nitricacid, is introduced into the leaching vessel 24 through a conduit 26.Sufficient nitric acid is provided to assure substantially completerecovery of the available manganese as soluble nitrates. About 1.5pounds of concentrated nitric acid per pound of manganese issatisfactory, i.e., a slight excess of nitric acid over that determinedby stoichiometric calculations for the formation of Mn(NO Theconcentrated nitric ,acid solution in the leaching vessel 24 alsocontains dissolved manganese as manganese nitrates in sufficientconcentration to provide the desired manganese impregnation on thesupports. We prefer that the supports contain from about 4- to about 8percent of manganese by weight. The acceptor and nitric acid areagitated as a slurry at about 50 to 200 C, for a sufficient period toassure that substantially all the manganese is converted to the solublenitrate form. At temperatures below about 50 C., the leaching processproceeds slowly. At temperatures above about 200 C., the pressurerequired to confine the reactants is excessive. About one-half to threehours has been a satisfactory residence period.

Following the leaching treatment, the slurry of supports in a nitricacid solution of manganese nitrate is withdrawn intermittently orcontinuously from the leaching vessel 24 through a valved conduit 27 andintroduced into a continuous pressure filter 28. The solution of nitricacid and manganese nitrate is recovered as filtrate through a conduit.29 and returned to a. storage vessel 30 providing a surge supply ofconcentrated nitric acid and soluble manganese salts. The acceptorsolids are recovered as a moist filter cake through a conduit 31. Thefilter cake contains acceptor particles having the desired manganesecontent, preferably from about 4 percent to about 8 percent by weight.

The moist acceptors are subjected to thermal drying, for example, in arotary dryer 32.

Hot gases, for example flue gases, are introduced into the dryer 32through a conduit 33 to supply heat for vaporization of the nitric acidsolution and decomposition of the manganese nitrate. When manganesenitrate is thermally decomposed, a residue of manganese oxide remains.The heating gases and dryer vapors are recovered from the dryer 32through a conduit 34 and are cooled and condensed in a condenser 35. Thecondensed liquids, principally nitric-acid solution, accumulate in asurge vessel 36 whence they can be recycled through a conduit 37 to thestorage vessel 30 for reuse in the process. N 'on-condensib1e gasesincluding the heating gases and nitrogen oxides are separately recoveredfrom the surge vessel 36 through a conduit 38 and are scrubbed withwater by a well-known technique for recovery of nitrogen oxides. Thenitrogen oxides thus recovered may be reused in the form of nitric acidsolution in the process.

Emanat'ing intermittently or continuously from the dryer 32 through aconduit 39 is a stream of reactivated acceptor containing manganeseoxide principally in the form of MnO the primary decomposition productof manganese nitrate. The acceptor is in a regenerated state (i.e.,sulfur has been eliminated) and also is in a reactivated state (i.e.,the manganese is readily available for combination with H 8). However,the acceptor is m a high state of oxidation and should be reduced priorto reuse in a desulfurization stage to avoid unnecessary consumption ofhydrogen. Accordingly, the acceptor preferably is returned to theregeneration zone 18 through conduit 39 to re-enter the recirculatingacceptor stream. Therein the oxidized acceptor will react with sulfidedacceptor undergoing regeneration to effect an oxygen transfer Since onlya minor portion of the recirculating acceptor Where desired, thereactivation process may also be employed to prepare fresh acceptorsolids. Particles of the support, preferably mullite, are introducedthrough a conduit 4t into the leaching vessel 24 along with thecorresponding quantity of manganese nitrate through a conduit 41. Theadded manganese nitrate enters the nitric acid solution and is uniformlysoaked upon the new as well as upon the reactivated acceptor particles.

In general, only a minor portion (from about 1 to 10 percent) of thetotal acceptor solids undergoing re.- generation will be subjected tothe reactivation treatment of the present invention. The major portion,from about 90 to 99 percent, of the recirculating acceptor solids willbe returned directly from the regenenation zone 18 to thedesulfurization zone 10 through the conduit 12.

Figure 3 graphically illustrates the effect of thermal exposure on lossof activity of acceptors impregnated with manganese oxide.

To calculate activity of an acceptor, a weighed batch of the acceptor isplaced in a container adapted to confine the acceptor in a bed underfluidizing conditions. A stream of gas having a predeterminedcomposition of hydrogen and H 8 is passed upwardly through the bedof'acceptor at a predetermined constant rate as a fluidizing gas.Usually the gas contains about 0.7 percent H 8 in hydrogen. The fractionof entering H S which reacts with the acceptor is measured. Initiallysubstantially all of the entering H S reacts with the acceptor.

Grams of H 8 reacted per hour Grams of unreacted MnO in the acceptor bedA freshly prepared acceptor has an activity which can be expressed asunity. The measured activity of any other acceptor under investigationcan be compared with that of the freshly prepared acceptor (expressed asunity)- v To develop the curves of Figure 3, a mullite carrierimpregnated with manganese oxide was used. The car-' rier contained 4percent of manganese. Samples of the acceptor were exposed to elevatedtemperatures for varying periods of time to illustrate the effect ofthermal exposure on activity loss. The activity of each sample wasdetermined and compared with that of a freshly prepared acceptor. Theactivity values (expressed as a percentage of the fresh acceptoractivity) are presented graphically in Figure 3 for each temperaturelevel of thermal exposure. I

The time required for a 50 percent less in activity would be about 5hours at 1600 F;, about 6 hours at 1500" F., about 87 hours at 1400 F.and about 210 hours at 1350 F. Since the desulfurization processes areoperated with an overwhelming excess of acceptor material, maintenanceof a maximum activity level is not requisite. Accordingly, fullrestoration of activity is not required during each regeneration cycle.Thus only a small portion of the recirculating stream of acceptor issubjected to the reactivating treatment of the present invention. Forexample, from about 1 to 10 percent by weight of the acceptor solidsundergoing regeneration would be exposed to the reactivation treatmentofthis invention.

To illustrate the efficacy of reactivation of the present process, anacceptor was selected comprising a mullite carrier containing 4.02percent by weight of manganese; By virtue of extensive thermaltreatment, this acceptor had an activity (under H s-absorbingconditions) only 20 percent of its original activity (under Hs-absorbing conditions). About 94 percent of themanganese in theacceptor was in the form of manganese sulfide.

This acceptor was placed in a closed vessel with sufficient concentratednitric acid (70 percent solution) to cover the particles. The contentsof the vessel were heated to 110 C. for four hours. Analysis of theaqueous phase showed that 99 percent of the manganese went into solutionfrom the supports; Subsequent heating of the nitric acid slurryevaporated the liquid constituent and decomposed the residual manganesenitrate to MnO The acceptor was reduced by treatment with hydrogen toconvert the manganese to MnO. The activity (under-H,S absorbingconditions) of the reactivated acceptor was indistinguishable from thatof freshly prepared acceptori Thus an acceptor which through thermaldeactivation had retained only 20 percent of its initial activity (whenfreshly prepared) was reactivated to a condition where its activityequaled its initial activity (when freshly prepared). Hence we havedemonstrated that the present invention counteracts the deactivationeffect accompanying thermal exposure of acceptors containing manganeseoxide.

According to the provisions of the patent statutes, we have explainedthe principle, preferred construction, and mode of operation of ourinvention and have illustrated and described what we now consider torepresent its best embodiment. However, we desire to have it understoodthat, Within the scope of the appended claims, the invention may bepracticed otherwise than as specifically illustrated and described.

We claim:

1. In a process employing solid acceptors for hydrogen sulfidecomprising manganese oxide impregnated on an inert support forsequentially absorbing hydrogen sulfide at temperatures above about 1100F. to form manganese sulfide, followed by oxidizing the manganesesulfide to manganese oxide by reaction with oxygen, the improvementwhich minimizes loss of the acceptors activity, under H S-absorbingconditions, comprising cooling a minor portion of the stream ofrecirculating acceptor in the manganese oxide form, contactingsaid minorportion with a concentrated solution ofmineral acid selected fromthe-class consisting of nitric acid, sulfuric acid and hydrochloricacid, at about 50 to 200 C. to leach out substantially all of themanganese in the form of soluble manganese salt, thereafter heating thesupports in contact with the manganese salts in acid solution tovaporize said acid solution, to deposit said soluble manganese salt'onsaid supports and to convert said manganese salt to manganese oxide, andrecovering said supports containing manganese oxide for reintroductioninto the recirculating stream of acceptors.

2. In a process employing solid acceptors for hydrogen sulfidecomprising manganese oxide impregnated on an inert support forsequentially absorbing hydrogen sulfide at temperatures above about 1100F. to form manganese sulfide, followed by oxidizing the manganesesultide to manganese oxide by reaction with oxygen, the Improvementwhich minimizes loss of the acceptors activity, under H S-absorbingconditions, comprising.

cooling a minor portion of the stream of recirculating acceptor in themanganese oxide form, contacting said in nitric acid solution tovaporize said nitric acid solution to deposit said manganese nitrate onsaid supports and? to convert said manganese nitrate to manganese oxide,

11 and recovering said supports containing manganese oxide forreintroduction into the recirculating stream of acceptors.

3. The improvement of claim 2 wherein the acceptor supports comprise aninert oxide selected from the class consisting of silica, alumina andsilica-alumina.

4. The improvement of claim 2 wherein the acceptor supports comprisemullite.

5. The improvement of claim 2 wherein the minor portion of saidrecirculating stream of acceptor comprises 1 to percent thereof byweight.

6. In the method of removing sulfur from particulate carbonizedcarbonaceous solids, which comprises preparin g an intimate admixture ofsaid carbonaceous solids and particulate acceptor solids comprisinginert carrier hav ing manganese oxide impregnated thereon, subjectingsaid admixture to treatment at a temperature above 1100 F. in thepresence of hydrogen gas until a portion of the initial sulfur has beenremoved from said carbonaceous solids and transferred to said acceptorsolids forming manganese sulfide, separating particulate acceptor solidscontaining manganese sulfide from low sulfur carbonaceous solids,recovering said low sulfur particulate carbonaceous solids as product,and restoring the H S-absorbing property of sulfided acceptor solids forrecirculation in the process, the improvement in the last-mentioned stepof restoring the H S-absorbing property of the sulfided acceptor solidscomprising subjecting said sulfided acceptor solids to a temperature of1300 to 1600" F. under oxidative conditions to remove sulfided sulfurtherefrom and reform manganese oxide thereby, recovering acceptor solidsas a recirculating stream having restored H 3 absorbing property,withdrawing a minor portion or" thustreated acceptor solids, coolingsaid minor portion and contacting same with a concentrated nitric acidsolution at about 50 to 200 C. to leach out substantially all of themanganese in the form of a soluble nitrate, recovering said supportstogether with said nitric acid solution containing manganese nitratetherein, thereafter heating the supports to vaporize said nitric acidsolution, to deposit said manganese nitrate on said supports and toconvert said manganese nitrate to manganese oxide, and recovering saidsupports containing manganese oxide for reintroduction into saidrecirculating stream.

7. The improvement of claim 6 wherein the inert carrier comprises anoxide selected from the class consisting of silica, alumina andsilica-alumina.

8. The improvement of claim 6 wherein the inert carrier comprisesmullite.

9. In a process employing solid acceptors for hydrogen sulfidecomprising manganese oxide impregnated on an inert support forsequentially absorbing hydrogen sulfide at temperatures above about 1100F. to form manganese sulfide, following by oxidizing the manganesesulfide to manganese oxide by reaction with oxygen, the improvementwhich minimizes loss of the acceptors activity, under fi s-absorbingconditions, comprising cooling a minor portion of the stream ofrecirculating acceptor in the manganese oxide 01m, contacting said minorportion with a concentrated nitric acid solution at about 50 to 200 C.to leach out substantially all of the manganese in the form of solublenitrate, introducing into the slurry of supports in nitric acid solutionadditional quantities of acceptor supports and manganese salts yieldingmanganese oxide when heated, to produce thereby additional solidacceptors for hydrogen sulfide, thereafter heating the supports incon-tact with the nitric acid solution containing the manganese nitrateto vaporize said nitric acid solution, to deposit said manganese nitrateon said supports and to convert said manganese nitrate to manganeseoxide, and recovering said supports containing manganese oxide forreintroduction into the recirculating stream of acceptors.

10. In the method of removing sulfur from particulate carbonizedcarbonaceous solids, which comprises preparing an intimate admixture ofsaid carbonaceous solids and particulate acceptor solids comprisinginert carrier having manganese oxide impregnated thereon, subjectingsaid admixture to treatment at a temperature above 1100 F. in thepresence of hydrogen gas until a portion of the initial sulfur has 'beenremoved from said carbonaceous solids and transferred to said acceptorsolids forming manganese sulfide, separating particulate acceptor solidscontaining manganese sulfide from low sulfur carbonaceous solids,recovering said low sulfur particulate carbonaceous solids as product,and restoring the H s-absorbing property of sulfided acceptor solids forrecirculation in the process, the improvement in the last-mentioned stepof restoring the H s-absorbing property of the sulfided acceptor solidscomprising subjecting said sulfided acceptor solids to a temperature of1300 to 1600 F. under oxidative conditions in a regeneration zone toremove sulfided sulfur therefrom and reform manganese oxide thereby,recovering acceptor solids as a recirculating stream having restored HS-abSorb-ing property, withdrawing a minor portion of thus-treatedacceptor solids, cooling said minor portion and contacting same with aconcentrated nitric acid solution at about 50 to 200 C. to leach outsubstantially all of the manganese in the form of a soluble nitrate,recovering said supports together with said nitric acid solutioncontaining manganese nit-rate therein, thereafter heating the supportsto vaporize said nitric acid solution, to deposit said manganese nitrateon said supports and to convert said manganese nitrate to manganeseoxide, and introducing said supports into said regeneration zone wherebythey are returned to the said recirculating stream in a reactivatedcondition.

11. The improvement of claim 10 wherein the particulate carbonizedcarbonaceous solids are carbonaceous briquets and the inert carrier is afinely divided fluidizable size inert support selected from the classconsisting of silica, alumina and silica-alumina.

12. The improvement of claim 10 wherein the particulate carbonizedcarbonaceous solids comprise char obtained by fluidized low temperaturecarbonization of caking bituminous coal.

References Cited in the file of this patent UNITED STATES PATENTS1,904,582 Watts Apr. 18, 1933 2,381,659 Frey Aug. 7, 1945 2,397,824Wanamaker et a1; Apr. 2, 1946 2,663,618 Babbitt et a1 Dec. 22, 19532,764,528 Sweeney Sept. 25, 1956 2,779,659 Koslov Jan. 29, 19572,824,047 Gorin et al Feb. 18, 1958 UNITED STATES PATENT OFFICECERTIFICATION OF CORRECTION Patent No 2,927,063

James Du Batchelor et al.

March 1, 196( It is hereby certified that error appears in the abovenumbered patent requiring correction and that the said Letters Patentshould read as corrected below.

Column 1, line 27, for "surfur" read sulfur column 6 line 17 for "Figure1" read Figure 2 s='.'-; column 7, line 11 for "from" read throughcolumn 11, line 54, for "following' read followed Signed and sealed this9th day of May 1961 I (SEAL) Attest:

ERNEST WQ SWIDER DAVID L. LADD Attesting Officer Commissioner of PatentsI UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent N02,927,063 March 1, 1960 James D, Batchelor et a1.

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 1, line 27, for surfur" read sulfur column 6, line 17, for,Figure 1" read Figure 2:5 column 7, line 11, for "from" read throughcolumn 11, line 54, for "following" read an followed Signed and sealedthis 9th day of May 1961.

(SEAL) Attest: I

ERNEST W SWIDER DAVID L, LADD Commissioner of Patents Attesting Officer

1. IN A PROCESS EMPLOYING SOLID ACCEPTORS FOR HYDROGEN SULFIDECOMPRISING MANGANESE OXIDE IMPREGNATED ON AN INERT SUPPORT FORSEQUENTIALLY ABSORBING HYDROGEN SULFIDE AT TEMPERATURES ABOVE ABOUT1100*F. TO FROM MANGANESE SULFIDE, FOLLOWED BY OXIDIZING THE MANGANESESULFIDE TO MANGANESE OXIDE BY REACTION WITH OXYGEN, THE IMPROVEMENTWHICH MINIMIZES LOSS OF THE ACCEPTORS ACTIVITY, UNDER H2S-ABSORBINGCONDITIONS, COMPRISING COOLING A MINOR PORTION OF THE STREAM OFRECIRCULATING ACCEPTOR IN THE MAGANESE OXIDE FORM, CONTACTING SAID MINORPORTION WITH A CONCENTRATED SOLUTION OF MINERAL ACID SELECTED FROM THECLASS CONSISTING OF NITRIC ACID, SULFURIC ACID AND HYDROCHLORIC ACID, ATABOUT 50 TO 200*C. TO LEACH OUT SUBSTANTIALLY ALL OF THE MANGANESE INTHE FORM OF SOLUBLE MANGANESE SALT, THEREAFTER HEATING THE SUPPORTS INCONTACT WITH THE MANGANESE SALTS IN ACID SOLUTION TO VAPORIZE SAID